Hey Atena so sorry for Guppy:( He was very happy betta:) I am glad that you going to have another one. If you will keep anything from Guppy's tank make sure you disinfect it. Do you need any tips on the disinfection?
Or you know i will just post it for you

http://www.bettafish.com/showthread.php?p=2036738
Be careful when you picking the betta make sure there is no sign of the disease. Can't wait for the picture.
Also btw just thought about it. You can quarantine new betta in the tank without any decorations for a few weeks just to make sure he is healthy . I don't want you to end up with disinfection's again.